All filtration systems are tasked with purifying some medium by separation of some suspended particles from the medium. An automated filtration system is a system that can remove suspended particles from liquid or gas and when required, regenerate or clean itself using some automated cleaning process. A semi-automated filtration system is a version of an automated filtration system with manual cleaning initiation and/or a human powered cleaning process. Aside from the above mentioned difference, in most cases the cleaning mechanisms are identical for both semi-automatic and automatic filters. (The present invention applies to both automated and semi-automated filters.)
Filtration is most often achieved using a size-discriminating medium. The gas or liquid being filtered is forced through the discriminating medium. In the process, suspended solids larger than the pores in the medium are trapped on the surface of the medium and in the medium itself. Some of the most popular filtration media are screens, granular beds (often sand), tightly packed disks, and wound fiber. Automated and semi-automated filters are capable of regenerating (cleaning) their filtration media.
The filtration and cleaning process for most automated water filters is as follows:                Filtration—Physical separation of suspended solids from a filtration medium. The stage begins with a clean filtration medium. As filtration progresses there is an increased buildup of filtered mass (filtrate) on the filtration medium.        Sensing—As filtrate builds up on the filtration medium, the filter's hydraulic resistance increases. This increase can be sensed by measuring the pressure differential between the intake and the outlet of the filter. Often a controller (mechanical or electronic) can sense the degree of resistance and trigger a cleaning cycle.        Cleaning—Clean filtration media are gradually clogged with the filtered particles (filtrate). As a result, the medium's hydraulic resistance increases. As filtration continues so does the buildup of filtrate and hydraulic resistance. Eventually a hydraulic resistance is reached where the filtration process is no longer economical. Automated filters clean their filtration media using a separation method such as, but not limited to, reverse flow or high pressure water jet. During the process the method is applied locally to a small portion of the filtration media surface and is gradually moved in such a way as to eventually cover the entire medium surface. One of the main reasons for this trajectory based process is that it is not viable to apply the separation method to the entire surface at once. Thus, the art of automated and semi-automated filter cleaning consists of two vital elements:        
1 The separation method—the method for removing the filtrate buildup on the filter medium, usually applied locally by means of a cleaning tip or head.
2 The scanning method—the method for generating a trajectory that produces an appropriate coverage of the entire filtration medium by the cleaning head with a given cleaning effectiveness radius.
The prior art in automated and semi-automated scanning methods consists mostly of helix type trajectories along a cylindrical surface. A cylindrical filtration medium, often made of woven screens, is usually cleaned using reverse flow through a nozzle. Such filters build a filtrate layer inside the cylindrical screen and are cleaned by moving a nozzle in a helical path along the surface of the cylinder. The nozzle is open to atmospheric pressure through a pipe and the pressure drop causes suction and the removal of the buildup on the screen. The helical path of the nozzle is achieved through the combined action of rotational and linear motion. Some filters coordinate the two motions very carefully using a screw to produce a very efficient cleaning process while others have no coordination at all. In all cases, the quality of the cleaning is influenced by the completeness of coverage and the “instantaneous contact time” (ICT), both a function of the trajectory. The coverage is determined by the path, while the ICT is determined by the speed of travel along the path.
All known prior art helix based scanning methods have severely limited ability to adjust the trajectory or none at all.
In the known prior art, there are no scanning methods for cleaning flat surfaces using combinations of two or more motions, nor are there scanning methods for cleaning cylindrical surfaces that combine two rotations or more, or any combinations of three linear and/or rotational motions.